Cavities with fluent material

ABSTRACT

A method for loading a fluent material, for example slurry explosive or cement grout, into a cavity, the material being fed through one end of a loading tube against a free double-acting piston in the loading tube and expelled through the same end into the cavity by pressurised fluid acting on the piston. The invention also includes the cavity loading apparatus.

United States Patent [1 1 Duff [ 1 Feb. 25, 1975 1 CAVITIES WITH FLUENT MATERIAL [75] Inventor: John Sweton Duff, Adrossan,

Scotland [73] Assignees: Imperial Chemical Industries Limited, London, England; Rock Fall Company Limited, Glasgow, Scotland 22 Filed: May 15, 1973 21 App1.No.:360,456

[30] Foreign Application Priority Data May 31, 1972 Great Britain 25492/72 [52] 11.8. Cl. 86/20 C, 102/23 [51] Int. Cl. F42b 3/00, F42d 1/00 [58] Field of Search 102/21, 22, 23; 86/20,

3,040,615 6/1962 Johansson et: a1 86/20 C 3,075,463 1/1963 Eilers et a1 102/21 3,188,906 6/1965 Beck 36/20 C 3,236,268 2/1966 Simpson 141/27 3,244,232 4/1966 Myers 166/63 3,696,703 10/1972 Fox 86/20 C FOREIGN PATENTS OR APPLICATIONS 226,128 2/1963 Austria 86/20 C 608,519 11/1960 Canada... 102/21 1,234,188 10/1960 France 141/27 Primary Examiner--Benjamin A. Borchelt Assistant Examiner-H. 1. Tudor Attorney, Agent, or FirmCushman, Darby & Cushman [57] ABSTRACT A method for loading a fluent material, for example slurry explosive or cement grout, into a cavity, the material being fed through one end of a loading tube against a free double-acting piston in the loading tube and expelled through the same end into the cavity by pressurised fluid acting on the piston. The invention also includes the cavity loading apparatus.

5 Claims, 5 Drawing Figures PATENTED H5825 I975 il CAVITIES WITH FLUENT MATERIAL This invention relates to a method and apparatus for loading cavities with fluent materials in blasting or civil engineering operations. The method is advantageous for loading cavities in underwater surfaces, for example, loading boreholes with slurry explosive for underwater blasting or loading underwater foundations with cement grout.

The use of slurry explosive in blasting operations is now widespread and it is common practice to load these explosives into boreholes in bulk by pumping through loading tubes as described, for example, in UK Pat. Specification No. 1,202,478. The slurry usually contains oxygen-supplying salt, for example, ammo nium nitrate, a sensitiser and optionally additional fuel suspended in a saturated solution of the oxygensupplying salt, the solution usually containing a dissolved polymeric or macromolecular thickening agent. The thickener is usually cross-linked in the explosive to stiffen the explosive to a thick gel and prevent segregation of the constituents. When the explosive is loaded by pumping, the cross-linking agent is not usually added until immediately before the slurry is fed into the loading tube since the fully cross-linked slurry cannot be readily pumped. Thus, the cross-linking process commences when the slurry is in the loading tube and is completed in the borehole. In normal operations on dry land the loading tube is sufficiently short for the slurry to reach the borehole before the cross-linking develops sufficiently to impair the pumpability, but where the holes are located under deep water the loading tube has to be appropriately longer giving increased risk of the slurry cross-linking in the tube. In underwater blasting the water head is often more than times the length of the borehole so that the loading tube may contain more than 5 times the amount of explosive re quired to charge the hole, the dwell time in the tube being correspondingly lengthened. Similarly, when a pumpable grout of hydraulic cement is being loaded into an underwater cavity the dwell time in the loading tube is increased with the risk of the cement setting in the tube. Clearly it would be beneficial to load the slurry or cement in discrete quantities as required for each borehole or a lesser quantity as appropriate to the rate of cross-linking or setting of the material. It has therefore been proposed to dispense the slurry in slugs through the loading tube using a gas or liquid under pressure to force the slurry through the tube, This method is difficult to control because it is difficult to avoid breaks in the slug, which, with explosives, can cause propagation failure.

It is an object of this invention to provide an improved method and apparatus for loading a cavity with a fluent material by which an underwater cavity can be reliably filled with a discrete uniform charge of fluent material. A further object is to provide an improved method and apparatus whereby an underwater borehole may be loaded with slurry explosive for underwater blasting.

In accordance with this invention, a cavity is loaded with a fluent material, for example, a slurry explosive or cement grout, by a method wherein the fluent material is loaded into a loading tube through one end of the loading tube against one side ofa double-acting piston, which is freely and slidably positioned within. and movable along the loading tube, and expelled through the same end into the cavity by applying a pressurised fluid through the other end of the loading tube against the other side of the piston to move: the piston along the tube.

The pressurised fluid is conveniently compressed air or water.

In putting the invention into practice, one end of a loading tube with a double-acting piston located within it is conveniently attached to a supply of fluent material, the desired quantity of fluent material is fed into the tube, thereby moving the piston along the tube, the said end of the loading tube is detached from the supply of fluent material and inserted into the cavity, and compressed fluid is fed into the other end of the loading tube until the said fluentmaterial is displaced from the loading tube into the cavity.

Preferably the end of the loading tube containing the fluent material is sealed with an end-stopper after it is detached from the supply of fluent material to prevent spillage of material during transfer to the cavity. The stopper should be removable by the pressure exerted on the fluent material to displace the fluent material from the tube. When the fluent material is an explosive material the stopper may advantageously be the explosive priming charge.

The invention also includes an apparatus for loading a cavity with a fluent material, the apparatus comprising a loading tube having means for attaching one end to a supply of fluent material and the other end to a supply of fluid under pressure, and a double-acting piston freely and slidably positioned within, and movable along the loading tube whereby fluent material in the tube against one side of the piston may be displaced therefrom by feeding fluid under pressure into the tube against the other side of the piston.

The loading tube is preferably flexible to facilitate its insertion into irregular cavities. It is advantageously made of synthetic plastics material, for example, polyvinyl chloride, polyethylene or polypropylene, preferably reinforced with a filamentary material. The tube filling operation is facilitated if the tube is made of transparent material.

The double-acting piston may be disposable and ejected with each charge of fluent material but preferably the loading tube is provided with a stop member at the end through which the fluent material is displaced, to prevent the piston being ejected. More preferably the loading tube has a piston stop member at each end. The stops provide the further advantage that when the piston reaches a stop member the pressure on the piston increases, and indicates that the loading tube is either charged or discharged.

The piston preferably comprises a body member with resilient sealing members at its ends. The body member may, for example, be made of rubber or synthetic plastics material and the sealing members may, if desired, be formed integrally with the body member. It is generally preferable for the piston body to be of a heavier material, such as a metal, for example, stainless steel, and the sealing members to be separate replaceable resilient sealing members of, for example, rubber, leather or synthetic plastics material.

The invention is further illustrated by the following description of one form of loading apparatus, and its use for loading an underwater borehole, which is described, by way of example only, with reference to the accompanying drawings wherein FIG. 1 shows diagrammatically in sectioned elevation a borehole loading tube being filled with slurry explosive;

FIG. 2 is a section of the piston of FIG. 1; and

FIGS. 3 to 5 show diagrammatically three stages of 5 the filling of a borehole with the apparatus shown in FIG. 1.

The loading tube in FIG. 1 is a long flexible hose of transparent reinforced plastics material having quick-clamping coupling spigot members 11 and 12 inserted one in each end. A double-acting piston 13 located within the tube 10 and is freely movable along the tube between the coupling members 11 and 12 which act as'piston stops'As shown in FIG. 2 the piston 13 is fitted with sealing washers 14. A flexible, rubber, annular sealing member 15 for sealing the space between the tube 10 and the borehole is fitted around the coupling member 12. In FIG. 1 slurry explosive 16 is being filled into a loading tube 10 by clamping the coupling member 11 to a mating socket coupling member 17 on a pipe 18 from a pump 19, and pumping the slurry from a supply thereof. When the desired quantity of slurry explosive appropriate for the charge in one borehole is filled into the tube 10, the coupling member 11 is disconnected from coupling member 17 and a pellet 20 of high explosive priming composition is inserted in the end of the member 11 to prevent spillage of explosive. A line of detonating cord 21 is attached to the primer pellet 20 for initiating the primer and explosive.

The end of the tube 10 is then inserted through a drill casing 22 into an underwater borehole 23 as shown in FIG. 3 with the detonating cord 21 leading from the primer to the surface. The coupling member 12 is connected to a compressed air supply line 24. The air pressure acting on piston 13 expels the primer pellet 20 and slurry explosive l6 flows from the tube 10 into the borehole 23. The pressure of the slurry explosive 16 on the annular sealing member 15 raises the tube 10 in the borehole (FIG. 4) as the slurry is expelled from the tube 10 into the borehole. When the piston 13 reaches the coupling member 11 (FIG. 5) the required charge is loaded in the borehole 23. The tube 10 and casing 22 are withdrawn from the borehole and the charge is ready for firing subsequently by detonation of the detonating cord 21. The tube 10 is then ready for connecting to coupling member 17 to receive a further charge of slurry explosive.

What I claim is:

1. In a method of underwater blasting wherein explosive fluent material is loaded into a borehole the steps of loading the fluent material from a fluent material supply into a loading tube through one end of said tube against one side of a freely-slidable double-acting piston positioned within and movable along said tube, detaching said tube from said fluent material supply, sealing the same end of said tube with an end stopper, inserting the same end of said tube into the borehole, displacing said end stopper from the' same end of said tube, and expelling said fluent material through the same end of said tube into the borehole by applying a pressurized fluid through the other end of said tube against the other side of said piston to move said piston along said tube.

2. A method of loading a borehole with fluent material as recited in claim 1 wherein expelling of said fluent material from said tube is accomplished by applying a pressurized fluid from the group consisting of compressed air and water.

3. A method of loading a cavity with fluent material as recited in claim 1 comprising the further step of withdrawing said loading tube from said borehole after all of said fluent material is displaced from said tube into said borehole.

4. In a method of underwater blasting wherein explosive fluent material is loaded into a borehole the steps of loading said explosive fluent material from a fluent material supply into a loading tube through one end of said tube against one side of a freely-slidable doubleacting piston positioned within and movable along said tube, detaching said tube from said fluent material supply, sealing the same end of said tube with an explosive priming charge end-stopper, inserting the same end of said tube into said borehole, displacing said end stopper from the same end of said tube and expelling said explosive fluent material through the same end of said tube into said borehole by applying a pressurized fluid through the other end of said tube against the other side of said piston to move said piston along said tube, whereby said priming charge end-stopper is contacted by said explosive fluent material.

5. A method of loading a cavity with explosive fluent material as recited in claim 4 comprising the further step of withdrawing said loading tube from said cavity after all of said explosive fluent material is displaced from said tube into said cavity. 

1. In a method of underwater blasting wherein explosive fluent material is loaded into a borehole the steps of loading the fluent material from a fluent material supply into a loading tube through one end of said tube against one side of a freelyslidable double-acting piston positioned within and movable along said tube, detaching said tube from said fluent material supply, sealing the same end of said tube with an end stopper, inserting the same end of said tube into the borehole, displacing said end stopper from the same end of said tube, and expelling said fluent material through the same end of said tube into the borehole by applying a pressurized fluid through the other end of said tube against the other side of said piston to move said piston along said tube.
 2. A method of loading a borehole with fluent material as recited in claim 1 wherein expelling of said fluent material from said tube is accomplished by applying a pressurized fluid from the group consisting of compressed air and water.
 3. A method of loading a cavity with fluent material as recited in claim 1 comprising the further step of withdrawing said loading tube from said borehole after all of said fluent material is displaced from said tube into said borehole.
 4. In a method of underwater blasting wherein explosive fluent material is loaded into a borehole the steps of loading said expLosive fluent material from a fluent material supply into a loading tube through one end of said tube against one side of a freely-slidable double-acting piston positioned within and movable along said tube, detaching said tube from said fluent material supply, sealing the same end of said tube with an explosive priming charge end-stopper, inserting the same end of said tube into said borehole, displacing said end stopper from the same end of said tube and expelling said explosive fluent material through the same end of said tube into said borehole by applying a pressurized fluid through the other end of said tube against the other side of said piston to move said piston along said tube, whereby said priming charge end-stopper is contacted by said explosive fluent material.
 5. A method of loading a cavity with explosive fluent material as recited in claim 4 comprising the further step of withdrawing said loading tube from said cavity after all of said explosive fluent material is displaced from said tube into said cavity. 